Significant Reduction in Bone Density as Measured by Hounsfield Units in Patients with Ankylosing Spondylitis or Diffuse Idiopathic Skeletal Hyperostosis.

Background: Multisegmental pathologic autofusion occurs in patients with ankylosing spondylitis (AS) and diffuse idiopathic skeletal hyperostosis (DISH). It may lead to reduced vertebral bone density due to stress shielding. Methods: This study aimed to determine the effects of autofusion on bone density by measuring Hounsfield units (HU) in the mobile and immobile spinal segments of patients with AS and DISH treated at a tertiary care center. The mean HU was calculated for five distinct regions-cranial adjacent mobile segment, cranial fused segment, mid-construct fused segment, caudal fused segment, and caudal adjacent mobile segment. Means for each region were compared using paired-sample t-tests. Multivariable regression was used to determine independent predictors of mid-fused segment HUs. Results: One hundred patients were included (mean age 76 ± 11 years, 74% male). The mean HU for the mid-construct fused segment (100, 95% CI [86, 113]) was significantly lower than both cranial and caudal fused segments (174 and 108, respectively; both p < 0.001), and cranial and caudal adjacent mobile segments (195 and 115, respectively; both p < 0.001). Multivariable regression showed the mid-construct HUs were predicted by history of smoking (-30 HU, p = 0.009). Conclusions: HUs were significantly reduced in the middle of long-segment autofusion, which was consistent with stress shielding. Such shielding may contribute to the diminution of vertebral bone integrity in AS/DISH patients and potentially increased fracture risk.

Reduced Bone Density Based on Hounsfield Units After Long-Segment Spinal Fusion with Harrington Rods.

BACKGROUND: Long-segment instrumentation, such as Harrington rods, offloads vertebrae within the construct, which may result in significant stress shielding of the fused segments. The present study aimed to determine the effects of spinal fusion on bone density by measuring Hounsfield units (HUs) throughout the spine in patients with a history of Harrington rod fusion. METHODS: Patients with a history of Harrington rod fusion treated at a single academic institution were identified. Mean HUs were calculated at 5 spinal segments for each patient: cranial adjacent mobile segment, cranial fused segment, midconstruct fused segment, caudal fused segment, and caudal adjacent mobile segment. Mean HUs for each level were compared using a paired-sample t test, with statistical significance defined by P < 0.05. Hierarchic multiple regression, including age, gender, body mass index, and time since original fusion, was used to determine predictors of midfused segment HUs. RESULTS: One hundred patients were included (mean age, 55 ± 12 years; 62% female). Mean HUs for the midconstruct fused segment (110; 95% confidence interval [CI], 100-121) were significantly lower than both the cranial and caudal fused segments (150 and 118, respectively; both P < 0.05), as well as both the cranial and caudal adjacent mobile segments (210 and 130, respectively; both P < 0.001). Multivariable regression showed midconstruct HUs were predicted only by patient age (-2.6 HU/year; 95% CI, -3.4 to -1.9; P < 0.001) and time since original surgery (-1.4 HU/year; 95% CI, -2.6 to -0.2; P = 0.02). CONCLUSIONS: HUs were significantly decreased in the middle of previous long-segment fusion constructs, suggesting that multilevel fusion constructs lead to vertebral bone density loss within the construct, potentially from stress shielding.

Surgical management of recurrent lumbar disc herniation and the role of fusion.

This systematic review was performed to evaluate the various operative management strategies for recurrent lumbar disc herniation (RLDH), including the efficacy of instrumented spinal fusion (ISF) at repeat discectomy, and whether the operative approach for repeat discectomy, minimally invasive (MID) or conventional open discectomy (CD), affected the outcomes. RLDH is one of the most common complications of lumbar discectomies. Whilst repeat discectomy is the standard procedure performed, the routine addition of ISF has been advocated to improve outcomes and prevent reherniation. A comprehensive search of the MEDLINE, EMBASE, CINAHL and Cochrane databases was performed. The measured outcomes included the rate of satisfactory clinical outcome, improvement in leg and back pain, Japanese Orthopaedic Association (JOA) recovery score, and complication rates. In total, 37 studies met our inclusion criteria, with 1483 patients. The rate of satisfactory outcomes was found to be statistically similar between the patients undergoing a discectomy with or without fusion (77.8% with ISF versus 79.5% without ISF; p=0.665). Back pain and JOA scores showed greater improvements in the patients undergoing discectomy and fusion, compared to discectomy alone. The rate of satisfactory outcomes was marginally higher in the patients undergoing MID compared to CD (MID 81.2% versus CD 77.5%; p=0.248). However, the leg pain improvement was similar. The postoperative back pain improvement was greater in the MID group (52.5% MID versus 36.3% CD), but with lower complication rates, specifically durotomies (MID 5.2% versus CD 15.3%; p<0.001). There is no evidence to recommend the routine addition of ISF in the management of RLDH. The data suggest that MID has lower complication rates than CD in the setting of RLDH, yet unequivocal evidence is lacking.

The impact of blood-borne viruses on cause-specific mortality among opioid dependent people: An Australian population-based cohort study.

BACKGROUND: Blood-borne viruses (BBV) are prevalent among people with opioid dependence but their association with cause-specific mortality has not been examined at the population-level. METHODS: We formed a population-based cohort of 29,571 opioid substitution therapy (OST) registrants in New South Wales, Australia, 1993-2007. We ascertained notifications of infection and death by record linkage between the Pharmaceutical Drugs of Addiction System (OST data), registers of hepatitis C (HCV), hepatitis B (HBV) and human immunodeficiency virus (HIV) diagnoses, and the National Death Index. We used competing risks regression to quantify associations between notification for BBV infection and causes of death. BBV status, age, year, OST status, and OST episodes were modelled as time-dependent covariates; sex was a fixed covariate. RESULTS: OST registrants notified with HCV infection were more likely to die from accidental overdose (subdistribution hazard ratio, 95% Confidence Interval: 1.7, 1.5-2.0), cancer (2.0, 1.3-3.2) and unintentional injury (1.4, 1.0-2.0). HBV notification was associated with a higher hazard of mortality due to unintentional injury (2.1, 1.1-3.9), cancer (2.8, 1.5-5.5), and liver disease (2.1, 1.0-4.3). Liver-related mortality was higher among those notified with HIV only (11, 2.5-50), HCV only (5.9, 3.2-11) and both HIV and HCV (15, 3.2-66). Registrants with an HIV notification had a higher hazard of cardiovascular-related mortality (4.0, 1.6-9.9). CONCLUSIONS: Among OST registrants, BBVs are a direct cause of death and also a marker of behaviours that can result in unintended death. Ongoing and enhanced BBV prevention strategies and treatment, together with targeted education strategies to reduce risk, are justified.

Opioid substitution therapy is associated with increased detection of hepatitis C virus infection: a 15-year observational cohort study.

BACKGROUND: Strategies are needed to enhance screening of hepatitis C virus (HCV) infection among people who inject drugs to improve engagement in HCV treatment, and stem the growing burden of HCV-related morbidity and mortality. METHODS: We linked routinely collected data on enrolment in opioid substitution therapy (OST) and HCV notifications. We calculated rates of incident HCV notifications, and compared rates in and out of OST. RESULTS: Following adjustment for sex, age and calendar period, rates of incident HCV notification were significantly higher during periods of OST, compared to periods out of OST (adjusted incident rate ratio: 1.91; 95% confidence interval: 1.86, 1.97). This effect was seen across multiple treatment periods. CONCLUSIONS: HCV screening in OST settings increases detection of HCV infection among people who inject drugs.

Examining the quality of name code record linkage: what is the impact on death and cancer risk estimates? A validation study.

OBJECTIVE: To examine the validity and impact of record linkage using name code compared to full name records. METHODS: A registry of 45,419 opioid substitution clients (1985-2007) was linked with national population-based death and cancer registries using registrant's name, date of birth, sex, state, postcode and date of death. Records were linked using full name and then using the first two letters of the given and surname (2×2 name code). Sensitivity and specificity were computed and regression analysis used to identify factors related to linkage accuracy. Standardised mortality ratios (SMR) and standardised cancer incidence ratios (SIR) were estimated. RESULTS: The sensitivity and specificity of name code compared to full name linkage were 65.31% and 99.91% for death records and 76.81% and 99.89% for cancer records. Registrants' age and sex and accuracy of the registries were associated with risk of false linkages. Death and cancer risks (SMR 6.98, 95%CI 6.77-7.19; SIR 1.16, 95%CI 1.08-1.24) were significantly under-estimated using name code linkage (SMR 4.39, 95%CI 4.23-4.56; SIR 0.92, 95%CI 0.85-0.99). CONCLUSION: Record linkage using 2×2 name code has low sensitivity but high specificity, resulting in conservative estimates of death and cancer risk. This may translate to meaningful differences in outcomes.

The importance of blood-borne viruses in elevated cancer risk among opioid-dependent people: a population-based cohort study.

OBJECTIVE: To quantify cancer risk in opioid dependence and the association with infection by the oncogenic blood-borne viruses (BBVs) hepatitis C (HCV), hepatitis B (HBV) and HIV. DESIGN: Cohort study. SETTING: New South Wales, Australia. PARTICIPANTS: All 45 412 adults aged 16 years or over registered for opioid substitution therapy (OST) between 1985 and 2007. Notifications of cancer, death and infection with HCV, HBV and HIV were ascertained by record linkage with registries. MAIN OUTCOME MEASURES: The ratios of observed to expected number of cancers, standardised incidence ratios (SIRs), and the average annual per cent change (AAPC) in overall age and sex-standardised cancer incidence. RESULTS: Overall cancer risk was modestly increased compared to the general population (SIR 1.15, 95% CI 1.07 to 1.23). Excess risk was observed for 11 cancers, particularly lung (4.02, 95% CI 3.32 to 4.82), non-Hodgkin's lymphoma (1.51, 95% CI 1.20 to 1.88) and liver (8.04, 95% CI 6.18 to 10.3). Reduced risk was observed for six cancers, including prostate (0.16, 95% CI 0.06 to 0.32) and breast (0.48, 95% CI 0.35 to 0.62). Individuals notified with HCV or HBV had a markedly increased risk of liver cancer; lung cancer risk was also increased in those with HCV. HIV was associated with an elevated risk of liver, anus and kidney cancer, non-Hodgkin lymphoma and Kaposi sarcoma. Cancer risk was not increased in individuals without a BBV notification, apart from pancreatic cancer (3.92, 95% CI 1.07 to 10.0). Cancer incidence increased significantly over time (AAPC 9.4%, 4.2% to 15%, p=0.001). CONCLUSIONS: BBVs play a major role in the cancer risk profile of opioid-dependent individuals registered for OST. To address the dramatic increasing trend in cancer incidence, the OST setting could be utilised for cancer prevention strategies.